Sipe blades for tire curing molds are well known in the art of tire manufacture. Such blades are conventionally made from a strip of metallic material, such as steel, stainless steel or brass. The strip of material is generally up to 1 mm thick.
The blades create sipes in a tire tread during the vulcanization step of a green tire in a curing mold. A sipe is generally understood to refer to a small slot or slit molded into a tread element of the tire that subdivides the tread surface and improves traction. Sipes are of small width, on the order of 1 mm or less, and they close or substantially close when located in the footprint of the tire, i.e., in the contact patch of the tire tread with a flat surface at zero speed and under normal load and inflation pressure. The sipes may extend circumferentially, laterally or diagonally about the tread in a straight, curved or zig-zag manner and may be as deep as the tread block and rib defining grooves. The sipes may pass through or cut one or both of opposing sides of a tread element or may be confined to its interior. Sipes are distinguished from tread grooves in that the grooves do not close up in the footprint of the tire, and generally have a width of at least 2 mm.
Sipes on the tread surfaces act as squeegees against road surfaces and thereby give the tires better traction, especially on slippery or wet roads. These sipes may vary in size and configuration to provide the desired effect. However, forming sipes of complicated and sophisticated shapes presents a challenge to the tire manufacturer.
In a typical tire building process, a tire assembly is placed into a mold with the tread strip positioned to abut a mold surface having a pattern therein corresponding to the desired tread groove/tread element pattern for the particular tire to be manufactured. A curing bladder is placed adjacent the interior of the tire assembly and expanded to force the tread strip against the mold surface thereby forming the tread pattern in the uncured tread strip. When sipes are to be formed in the tread elements, sipe blades are affixed to the mold surface such that the blades are forced into the uncured tread strip as the tread strip is forced against the mold surface. After shaping the tread, the tire assembly is then cured or vulcanized in the mold to permanently set the tread pattern. This overall process is referred to as shaping and curing.
After curing, the sipe blades must be separated from the cured tire, thereby leaving the sipes formed in the tread elements. The more sophisticated the shapes of the sipe blades are, the more difficult it is to remove the sipe blades from the cured tire. In addition, damage to the tread elements may occur upon removal of the sipe blades, which compromises the integrity of the tire tread.
There is thus a need to develop a way to form sipes in a tire tread, wherein the sipe blades are easily removed from the cured tire and do not damage the tire tread.